Joan tried it once 20 years ago, only to walk out midway through the £300 treatment.
“Botox is disgusting,” she half-snarls. “It was agony. It’s far better to just take care of your skin and get a few lines, just like Helen Mirren, Judi Dench and, well, me. You have to embrace what happens.
“It’s like that 60:16 thing – 16 from behind, 60 from the front. I don’t want that.
“Anyway, I don’t want to pretend to be 35, I can’t pretend to be 35.”
Here she pauses and raises a perfectly arched eyebrow, before adding: “Well, maybe in a good light...”
Witty, waspish and, when gushing about her husband Percy Gibson, surprisingly warm, the mother-of-three is wonderful company.
Unlike today’s media-trained Hollywood automatons, Joan is not scared of expressing an opinion. And, despite her glamorous appearance, the former Dynasty star is not averse to getting her hands dirty either.
“People seem to have this perception of me, that I basically wake up like this in full make-up,” she smiles.
“I spend time every morning on our terrace here in LA, watering the flowers and beheading anything that needs to be beheaded.
“Then I’ll come back in and tidy up – I’m a massive tidier-upper, and always plumping up cushions and emptying out ashtrays.”
Joan, of course, is not the smoker, having kicked the habit 10 years ago, meaning Percy is the sole puffer in the house.
When I ask Joan if she has a personal chef, she laughs in my face. Not in a Towie kind of way, but elegantly. Everything she does is elegant.
“A chef? Who could afford a chef?,” she splutters. “I cook – I mean, I raised three children so why wouldn’t I? I do a great spaghetti Bolognese.
“We only have a maid in three times a week. I do it the rest of the time. We like our privacy. I seem to have this reputation of being some sort of diva, but I’m really not. Well, not really.”
After first making a cameo appearance in ITV show Benidorm, Joan recently signed up to appear in her third series. In it, she plays feisty hotel boss, Crystal Hennessy-Vass.
While the comedy is a tongue-in-cheek celebration of all things chav, in real life Joan does not strike me as the velour tracksuit-wearing type.
“I love the whole chav culture, it’s hilarious,” she laughs. “I mean, I don’t want to be a part of it but it’s hilarious.”
And what about the tracksuit – does she own one?
“Velour? No. But I do own a tracksuit, actually. It’s cashmere, £99, from Marks & Spencer.”
Earlier this year Joan and Percy had their 13th wedding anniversary after marrying at Claridge’s in 2002. She says: “Thirteen years is wool, so he bought me a beautiful woollen cap edged in fur, and I bought him beautiful cufflinks... not edged in fur.”
While the actress doesn’t have a brilliant track record with men – as divorces from Maxwell Reed, Anthony Newley, Ron Kass and Peter Holm testify – Percy, it seems, is a keeper.
They are, she says, together “24 hours a day” – indeed, Percy is lunching in the same West Hollywood restaurant as us, four tables away – and trust is key to their relationship. And separate loos.
The couple also have open access to one another’s phones. “We share everything, we have no secrets,” she reveals. “We look at each other’s emails, we look at each other’s phones if we want.
"Here in LA we have to share a bathroom, which is hard, but we do have different loos. Marriage does take a certain amount of work, and you have to be considerate.
“A lot of women get married and after the initial flow of pheromones wears off, the husband will go to the pub and not come home, or he’ll start playing video games.
“But we interact all the time, we never stop talking... except at night when we love to watch television together.
“Our current obsession is Banshee, which my sister, Jackie, put me on to. It’s very sexual and violent. There’s a lot of blood, and full-frontal sex. It’s basically like porn.”
You see, Joan Collins really isn’t like most 81-year-olds. The award-winning actress, who recently launched her own Timeless Beauty make-up range, is tireless at work and at home.
On the secrets to a successful union, she adds: “The most important thing is to know your spouse really well. We do romantic things, and we leave little notes for each other.
“He likes to do things for me more than he lets me do things for him, although I do love to bring him coffee in the morning after he’s kept me up all night, snoring.
“Percy is the most kind and gentlemanly man.
“God forbid I should try and open a car door for myself, or carry a package. It’s wonderful. He is beyond fantastic with my family, they all adore him. He’s Prince Percy.
“There’s not the slightest question that we would ever break up.”
While it is hard to imagine Joan ever being, or looking, less than immaculate – her hair and make-up are flawless, her monochrome outfit perfectly put together, her manicure pristine – she does, she admits, have her faults.
She expands: “We have things that irritate us about the other.
"Percy hates the fact I’m so quick; I wake up and am up, on the phone, doing my make-up, making coffee, doing three things at once. He’s slower to get going.
“He only drives with one hand and that irritates me. Of course we have little spats, it would be unnatural if we didn’t, but we adore each other.
“I think the biggest rows we’ve had are about my impatience and intolerance. Percy is polite, more so than me.
“Oh, and we row a bit about the fact he won’t exercise, whereas I try to go at least three times a week. But if we do row, we always make up.”